Snap acting thermostatic switch



Feb. 23, 1965 M. D. STAHL 3,170,998'

SNAP ACTING Tl-IERMOSTATIC SWITCH Filed Jan. 31, 1962 Fig. 4

I2 49 5 4a 0&0

Fig.5

United States Patent of Ohio Filed Jan. 31, 1962, Ser. No. 170,201

7 Claims. (Cl. 200-67) The present invention relates to electric irons and more particularly to a snap acting thermostatic switch therefor.

This is a continuation-in-part of my copending application, Serial No. 34,491, filed June 7, 1960, and now abandoned.

Thermostatic switches for electric irons are old and well known but are usually of the on-off type in which the contacts are made and broken slowly. Such switches are entirely unsuitable for high voltages because of the excessive arcing at the contacts as they are made and broken.

Snap acting switches are also old and well known but must be positively moved to both their off and on positions which require special arrangements of thermostats for both opening and closing such switches.

According to the present invention a normally closed snap acting switch is provided which is opened by a thermostat with a snap action when the sole plate reaches a definite temperature and automatically closes also with a snap action when the sole plate temperature is reduced below a definite point.

According to the present invention, the switch is a complete entity before it is assembled to the sole plate but no individual part thereof is a snap acting device in and of itself. j l

The snap acting movement is produced by first and second active spring like elements so assembled that the switch contacts .will always return to closed position with asnap action when the actuating pressure is, released and will open with a snap action when pressure is applied in an upward direction by a thermostat or other actuator to the free end portion of the first of said elements.

According to the invention neither of the! two active elements is snap acting in andof itself but becomes snap acting only when assembled andheld in the proper relationship. g a

Contrary to the usual snap acting switchin which the actuator must be manually or otherwise actuated to return the switch to its on position, the first of the active elements of the present invention is biased-or prestressed so as to return the switch to'its on" position withv'a snap Y action when the actuating pressure is released.

The first active elem'entisfa stamping of spring'ma; terial generally rectangular in form with closed ends.

One end is formed with an opening for attaching it to a fixed support while theother end is formed with a nar- 3,170,998 Patented Feb. 23, 1965 "ice the backwardly turned hook on the free end of the cenpost extending upwardly from the sole plate. A fixed contact issupported on the post and extends outwardly therefrom beneath and parallel to the first active element.

A metallic support having a threaded aperture for receiving the temperature adjusting screw of the manual control for the iron is supported on top of the post and extends outwardly over and parallel with the first acitve element. "The lower end of the adjusting screw contacts the central tongue of the first active element, it being noted that movement of that tongue does not affect the position of the remainder of the first active element.

With the first active element and the fixed contact mounted on the post as above described the second active element may be assembled by positioning its contact end between the fixed contact and the stop with the contacts facing each other, positioning the end of the central tongue of the second active element in the hook on the end of the central tongue of thefirst active element and pushing on the second active element to place the curved central tongue of the second active element under compression untilthe upturned ends of the sides of the second active element clear the shoulders formed by the legs of the first active element to each side of the tang and then move the end of the second active element upwardly to engage the'inside corners of the sides of the second active element tive element.

The second active element will then be detachably engaged with the freeend of the first active element but the parts will be under stress to hold the's'econd active element in position with the movable contact on its end in contact with the fixed contact mounted on the post, with the stress of the sides of the first active element being biased tohold the contacts in engagement.

The thermostat is positioned to'push upwardly on a tang at the freeend of the first active. element until the line between the contacts and the'pivot between the legs of the two active elements passes the pivotbetween the tongues of the two active elements at which time the free Other objects and advantages of the present invention will'b'ecome apparent as the description proceedswhen taken in connection with the accompanying drawings in l which:

row downturned tang, the shoulders at the sides of v the v tang forming pivots for the second active element as will later appear. A central tongueextends from the fixed" endof the stamping and is providedwith a downturned' backwardly extending hook shaped portion which forms a pivot point for the tongue of the second active elestop for the switch arm .as will later appe The second active element is also in the form of a rectangular stamping of spring material having'closed ends and a central tongue-. The closed end from which the legs of the first active element. 'The central tongue is a bowed downwardly-"audits free end forms a pivot with the switch ofFIG. 1, Y i FIG. 5 ,is a sectional viewof second active element of the switch of FIG. 1 taken on line looking in the direction of the arrows, FIGS. 6, 7" and 8 show details of two rnodifications of the pivotal connection between the two active elements;

. ment as will appeardater. A small stop tongue is stamped downwardly from the central tongue to form a FIG.-l is a side view partly in section of the switch of the invention,

FIG- 2 is a top view of the first'active element of the switch of FIG. 1,

FIG.-3 is a sectional 'view' of the first active element FIG. 2and looking in the directiontaken on line 3-3 of of the arrows,

FIG. 4 is atop view of the s'econdactive element of 5 5 of FIG. 4 and of the switch.-

Referring particularly to FIGS. incliisive the switch 1 isigenerally'indicated by the reference numeral 10, the first activeelement by the reference numeral 11 and the second activeelement by the reference'numeral 12.

I 'Thegswitch 10 is m unted onthe sole plate'13 by means i V with the shoulders of .the first acplate about the opening 16.

. Mounted on the sleeve 17 above the flange 18 is a bimetallic element 19 and a heat conductor 20 which conducts heat from the flange l8 outwardly along the length of the bimetal 19 to prevent overshoot when the iron is firstv energized.

On top of the bimetal 19 and surrounding the sleeve 17 is a disc 21 of ceramic insulating material insulating the bimetal 19 from a metallic strip 22 which extends outwardly over and parallel to the bimetal 19 and carries a fixed contact 23. On top of the strip 22 in the order named is a metallic take-off lug 24, another ceramic disc 25, a second metallic take-oil lug 26, the end 27 of element 11, a ceramic disc 23 and a metallic support 29. A sleeve 39 of ceramic material separates the metal lic sleeve 17 from the metallic members 22, 24, 26 and 11 so as to electrically insulate those members from the post 17.

The upper end of the sleeve 17 is provided with a; swaged over upper flange 31 which aiong with the flange 18 renders the switch 16 a unitary structure which may be handled independently of the sole plate 13 so that the switch 16 may be calibrated before being attached to the sole plate 13.

The first active element 11 of the switch of the v present invention is a rectangular stamping of spring The closed end 31 of element 11 is provided with a tang 36, adapted to be contacted .by an insulating button 3-? carried by the free end of bimetal 19 as shown in F6. 1.

The tang 36 is narrower than the main body of element 11 so as to form shoulders 38 which form pivot points for the element 12 as will presently appear. The tang 36 is connected to the outer ends of sides 32 by upwardly inclined spaced apart strips 39 with a space formed between them in which the downturned end 40 of tongue 33 is positioned. The lower ends of strips 39 form the shoulders 38.

The end 49 of tnogue 33 is bent inwardly to form a hook41 which forms apivot point for the free endof tongue 42 of element 12 as will appear. The tongue 33 of element 11 is also provided with a raised portion 43 which coacts -with a ceramic pin 44 positioned in a bore in the lower end of the adjusting screw 45 carriedby the support 29.

' I The active element 12 is also a closed end rectangular body made from light spring steel. I-t'comprises a closed end 46 which carries the movable contact 47, the tongue 42 which is bowed downwardly as shown in FIG; 5, an upwardly bent closed .end 48 and sides 49 connecting the cooperate with the shoulders 38 of element 11 when the element 12} is snap acting in and of itself but when assemclosed ends 46 aud ts. The convex corners 59 connecting the closed end 48 with the sides 49 form pivot points which parts are assembled as will presently: appear. The end.-

bled as shown'in FIG 1 a snap, acting switch is forrned.

The element 11 forms a permanent partof the-post 15 l by"placing.its closediend :27 over the.ceramictsleeve 3t)- hector 24.

with the perimeter of the opening 35 surrounding the sleeve before the flange 31 is peened over. The end 46 of'element 12 with the movable contact 47 facing downwardly is then inserted between the fixed contact 23 and the tab 34 and moved backwardly far enough to engage the end 51'of tongue 42 in the hook 41 to form a pivot point 52. The element 12 is then moved to the left as viewed in FIG. 1 to place the tongue 42 in compression until the corners 54) of the closed end 48 can be moved upwardly to engage over the shoulders 35% to form pivot points The element 12 is then released and will be self supporting, the tongue 42 being under compression and the sides 49 under tension. 7

The sides 32 of element 11 will be under compression 32 of the element 11 are biased downwardly or stressed to hold tle closed end or tang 36 downwardly unless pressed upwardly by the button 37 on the end of the bimetal 19 and that is true regardless of the setting of the adjusting screw 45 which acts on the central tongue 33 and raises and lowers the hooked end 41 andthus the pivot point 52 to alter the point at which the switch 10 snaps to its ofi position.

v 7 Operation The contacts are normally closed when the iron is cold and the bimetal 19 is down so that the button 37 is free of or just in contact with the tang 36. As the sole plate 13 heats up the bimetal l9 flexes upwardly and the button 37 pushesthe tang 36 and pivot points 53 upwardly while the pivot point 52 remains stationary because the tongue 33 is held stationary by contact with the button 44.

Upward movement of the pivot points 53 will slowly continue until the. points 53 are slightly above point 52 at which time the end 46 'of element 12 will move upwardly against tab 34 with a snap action and separate the movable contact 47 from fixed contact 23 with a snap action.

The sole plate 13 will then begin to cool and the ametal 19. to flex downwardlyto move the button 37 downwardly. The tang 36 will follow because the sides- I Thus according tothe present invention the contacts are both openedand closed with a-snap action and it is not necessary'to provide a separate or special arrangement between the thermostat and switch to positively move a snap acting deviceto or from its overcenter positions, or in prior artswitches. i I 1 {It is to be noted'that the circuit through the switch is from connector 26, active element 11, pivots 53, active element 12,;c0ntacts 4-7 and 23, spring arm 22and con- Thusthe pivots 53 are current conducting. In certain conditions of use, .as in steam irons; the.

pivots53 may become corroded and thus unsatisfactory,

For such usagesjthemodifications of FIGS. 6, 7 and 8 may be used; Where the parts are the same they have: been given same reference numerals.

v In FIG. 3 ajumper or pig tail 61 is connected between the upturned end 43 of element 12and the tang 36 of; element 11 so that current'is conducted between the two;

active elements 11 and 12 independently of thejoints 53; In some usages it 'maynot be convenient'or -practical to providefa separate jumpenorpigtail in which case the'; two active elements 11 andalil ca'njhe spot welded to ga o' minat the pivgt fii an -r lyy n thefle ure.

of the metal of the elements to provide the equivalent of the pivots.

In that case the arrangement of FIGS. 6 and 7 may be used. The upstanding end 48 of element 12 is merely bent down on top of the tang 36 of element 11 as shown at 36' and 48 and the two spot welded together at 61. Thus the switch arm 12 will be cantilever mounted on the end of element 11, which is substantially the same as a pivot mounting and which eliminates the corrosion problem of the actual pivot joints as disclosed in FIG. 1.

In the claims where the terms pivotal attaching means, pivoted joints, pivotal connection, pivot points, pivotal engagement, etc. are used it is intended that those terms will include a construction wherein the elements 11 and 12 are connected in cantilever fashion by being welded together and the flexing of the metal of the elements forms th pivot.

While I have shown and described but three embodiments of my invention it is to be understood that those embodiments are to be taken as illustrative only and not in a limiting sense. I do not wish to be limited to the particular structure shown and described but wish to include all equivalent variations thereof except as limited by the scope of the claims.

I claim:

1. A snap acting switch comprising first and second strip type elongated spring elements lying in substantial spaced parallelism with each other, each of said elements including compression and tension members, means for supporting one end of the first of said elements so that its other end is free to flex transversely, pivotal atttaching means for connecting one end of the second of said elements to the free end of the first of said elements, said pivotal attaching means including pivoted joints between the respective compression and tension members of said elements in such manner as to place said compression members under a compressive stress and said tension members under a tension stress, stops positioned on opposite sides of the non-pivoted end of said second element and so related to said pivotal attaching means that the free end of said second element moves back and forth between said stops with a snap action upon back and forth movement of the pivotally connected ends of said elements, one of said stops comprising a fixed contact, and a movable contact carried by the nonpivoted end of said second element for cooperation with said fixed contact.

2. A snap acting switch according to claim 1 in which said pivotal attaching means includes two spaced apart pivot points so arranged that the non-pivoted end of said second element will snap back and forth between said stops as said pivot points pass their point of alignment with said movable contact.

3. A snap acting switch comprising first and second closed end strip type spring elements each having a pair of parallel side pieces and a central tongue extending from the closed end thereof, said elements lying in substantial parallel relationship with each other with the ends of the side pieces of the first element forming a pivotal connection with the ends of the side pieces of the second element and the end of the central tongue of the first element forming a pivotal connection with the end of the tongue of the second element, the pivotal connection between said side pieces being laterally olfset from the pivotal connection between said tongues and said elements being under lengthwise stress such that their closed ends tend to move away from each other, a support for the closed end of said first element, a movable contact carried by the closed end of said second element, a fixed contact carried by said support below said movable contact, a stop positioned above the closed end of said second element, the arrangement being such that movement of said pivotal connections past their point of alignment with said movable contact in either direction will snap the free end of said second element back and forth between said stop and fixed contact to both open and close said contacts with a snap action.

4. A snap acting switch comprising, a support, a first strip type spring element having a closed end fixed to said support and extending outwardly therefrom, said first element including a pair of parallel side pieces and a central tongue extending away from the closed end thereof, a second strip type closed end spring element, including a pair of parallel side pieces and a central tongue extending away from the closed end thereof, said second element being positioned below said first element with its closed end adjacent said support and carrying a movable contact on its lower face, a fixed contact carried by said support below said movable contact, a stop positioned above the closed end of said second element, the outer ends of the side pieces of the first and second elements being in pivotal engagement with each other, the free ends of the tongues of said first and second elements being in pivotal engagement with each other at a point spaced from the pivotal engagement of said side pieces and said elements being under lengthwise stress such that said movable contact is normally held in contact with said fixed contact and movement of the outer ends of said side pieces to move the points of pivotal engagement past their line of alignment with said movable contact in either direction will snap said contacts to open and closed positions.

5. A snap acting switch according to claim 4 including a bimetallic element for moving the outer ends of said side pieces to open said contacts and means acting on the tongue of said first element to vary the position of the point of engagement between said tongues to thus vary the temperature at which said contacts are opened without affecting the ability of the side pieces of said first element to close said contacts when the bimetallic element cools oil.

6. A snap acting switch according to claim 4 in which each of said pivotal engagements is in the form of a pressure contact joint between said elements and said second element is supported on the outer end of said first element by the stresses within said elements.

7. A snap acting device comprising, first and second strip type elongate spring stampings slotted lengthwise to provide compression and tension members, a post sup porting one end of said first stamping so that its other end is free to flex transversely, means for detachably and pivotally supporting one end of said second stamping on the free end of said first stamping with the other end of said second stamping free to move transversely and positioned laterally of said first stamping adjacent said post and spaced stops positioned on opposite sides of the free end of said second stamping to permit transverse movement thereof, said detachable supporting means including laterally spaced coacting abutments between the respective compression and tension members arranged to place said members under compressive and tension stresses so that the free end of said second stamping normally rests against one of said stops and as the free end of said first stamping is flexed transversely one of said abutments moves past the other to cause the free end of said second stamping to snap against the other of said stops with a snap action.

References Cited in the file of this patent UNITED STATES PATENTS 2,087,024 De Zotell July 13, 1937 2,157,156 Abendroth May 9, 1939 2,236,699 Riche Apr. 1, 1941 2,417,169 Kaminky Mar. 11, 1947 2,728,826 Lauder Dec. 27, 1955 2,859,305 Happe Nov. 4, 1958 3,004,124 Huffman Oct. 10, 1961 FOREIGN PATENTS 187,087 Austria Oct. 10, 1956 

1. A SNAP ACTING SWITCH COMPRISING FIRST AND SECOND STRIP TYPE ELONGATED SPRING ELEMENTS LYING IN SUBSTANTIAL SPACED PARALLELISM WITH EACH OTHER, EACH OF SAID ELEMENTS INCLUDING COMPRESSION AND TENSION MEMBERS, MEANS FOR SUPPORTING ONE END OF THE FIRST AND SAID ELEMENTS SO THAT ITS OTHER END IS FREE TO FLEX TRANSVERSELY, PIVOTAL ATTACHING MEANS FOR CONNECTING ONE END OF THE SECOND OF SAID ELEMENTS TO THE FREE END OF THE FIRST OF SAID ELEMENTS, SAID PIVOTAL ATTACHING MEANS INCLUDING PIVOTED JOINTS BETWEEN THE RESPECTIVE COMPRESSION AND TENSION MEMBERS OF SAID ELEMENTS IN SUCH MANNER AS TO PLACE SAID COMPRESSION MEMBERS UNDER A COMPRESSIVE STRESS AND SAID TENSION MEMBERS UNDER A TENSION STRESS, STOP POSITIONED ON OPPOSITE SIDES OF THE NON-PIVOTED END OF SAID SECOND ELEMENT AND SO RELATED TO SAID PIVOTAL ATTACHING MEANS THAT THAT THE FREE END OF SAID SECOND ELEMENT MOVES BACK AND FORTH BETWEEN SAID STOPS WITH A SNAP ACTION UPON BACK AND FORTH MOVEMENT OF THE PIVOTALLY CONNECTED ENDS OF SAID ELEMENTS, ONE OF SAID STOPS COMPRISING A FIXED CONTACT, AND A MOVABLE CONTACT CARRIED BY THE NON-PIVOTED END OF SAID SECOND ELEMENT FOR COOPERATION WITH SAID FIXED CONTACT. 